Field of the Invention
The present invention generally relates to systems and methods for distributing power and more specifically relates to systems and methods for distributing power using photovoltaic resources and battery energy storage to address intermittency needs and make renewable energy resources more reliable by using shifting.
Description of the Related Art
Renewable resources are becoming more and more available and affordable due to the development of technology and the enactment of government policies. Renewables and specifically photovoltaics (PV) are playing an ever increasing role in the resource mix for utilities across the nation. Many of these resources pose new integration challenges compared to traditional power generation. Electric utilities are required to deliver reliable power to customers and must operate utility grids within strict voltage limits. As renewable energy becomes a larger player amongst the resources supplying energy to these grids, issues begin arising due to the intermittent nature of these resources. The output from solar power can align reasonably well with daytime consumption on an electricity grid, thereby reducing the need for new fossil fuel power stations. However, high penetration PV, can lead to voltage instability due to intermittencies related to cloud cover. The output of PV is also generally noncoincident to utility system load peaks. If PV power is injected into a power system directly on a large scale, the PV power may produce issues related to dispatchability, reliability and stability. It may be desirable to filter out the highest rate transitions, and also avoid significant lag with respect to current power production.
Computer models of local utility grids were first developed to further understand integration of the batteries and PV. The results of actual field operation, combined with the underlying models are presenting a clear path in terms of optimizing battery size, and control algorithms, as well as offering a benchmark for measuring the benefits of battery storage.
Intermittent renewables present a challenge to utility system operations. Renewable Portfolio Standards mandate levels of renewable resources, and associated variations in power production that were not contemplated in traditional system designs. Distribution systems are designed to deliver power from the transmission system to utility customers. The design intent of distribution systems is to keep voltage and frequency levels within standard limits at all times for the utility customers. However, these systems have traditionally been designed for one-way power flow and are now being affected by large placements of PV. PV is appearing on the distribution grids, more so than on the transmission grids, due to modularity, associated costs of integrating large systems as well as tax incentives favoring customer and smaller utility owned sites. Various storage solutions are becoming a much needed component in recent Smart Grid demonstration projects. There is currently a need for an energy storage system that both can smooth and shift PV resources and thus lessen the effects of intermittency of PV and its effects on distribution systems.